Furnace shaft construction



Filed Jim 6, 1948 C. W. NICHOLS ETAL FURNACE SHAFT CONSTRUCTION 2Sheets-Sheet l I NVENTORS. CHARLES W. NICHOLS.

, osHuA GREENSPAN.

By UMJL,

ATTORNEYS.

Get, 4, 1949., c. w. NICHOLS Ema.

FURNACE SHAFT CONSTRUCTION 2 SI ieets-Sheet 2 Filed Jan. 6, 1948 N; m Lm V fi M m m mNR m W M 5% E H i M MJU c w hollow shafts used in suchfurnaces.

Patented Oct. 4, 1949 UNI TED STATES PATENT OFFICE v a FURNACE snrm'reossmvcnosii Charles W. Nichols, West"0range,and-Joshua Greenspan,.Nutley, N. Jgas'si'g'nors tozNichols Engineering & Research Gorporation-New York, N. Y., a corporation of Delaware Application January 6,1948',Serial 1 10.772

8 Claims. 1 This invention relates to roasting furnaces, and moreparticularly to'the construction of rotatabl Roasting furnaces ofthischaracter customarily are composed of a plurality of superposed roastinghearthswhich are contained within a cylindricalhousing and which arenormally provided with a central rotatable hollow shaft having hollowrabble arms attached' radially thereto. The shaft has an inner passagethrough which cooling air is circulated to inner passages in the rabblearms, returning through outer passages in the rabble arms to an outerpassage Within the shaft. Shafts as used heretoforein'such constructionshave been made in sections, each of which has comprised a singlecasting, including integrally the inner and outer tubular membersthereof. These members usually are interconnected by means of aplurality'of integral-webs. This integral construction'has variousdisadvantages, as

'will be pointed out hereinafter.

-I n accordance with the present invention a construction is providedhaving a hollow rotatable shaft comprising separate inner and outertubular members which, if desired, may be formed of dissimilar metalsandjwhich accomplish certain additional advantages, to appear more fullyhereinafter.

Various other objects, features and advantages of our invention will be'apparent from the detailed description when the same is read inconnection with the accompanying drawings. It is to be expresslyunderstood, however, that the drawings arefor purposes of illustrationonly and are not intended as a definition of the limits of theinvention, reference for this latter purpose being had to the appendedclaims; Inthe drawings: p r V a Fig. 1 is a sectional front elevation ofa typical portion of a roasting furnace of a type in which our inventioncanbe used, the section being taken substantially alongthe vertical axisthereof;

Fig. 2 is a horizontalsectional view of a rotat able furnace shaftembodying our invention, the section being taken substantially on line22 of Fig. 1;

Y Fig. 3 is an enlarged side elevation,in section with parts brokenaway, of the shaft shown in Fig.2;

Fig. 4; is a fragmentary'enlarged detailedview in section of twoportions of an inner tubular section showing a severance of saidportions and a seal therebetween; j 1

Fig. 5 is an enlarged detailed top. view-oi a 2 pair or cooperatingfingers and lugs upon the inner andouter shafts prior" to forming's'amefor therecep-tioncfaconnectinglmember;

Fig. 6 is a top view 'of'the fingers'shownin Fig. 5. with a connectingmember "shown in section "thereb'etwe'en; and-* f Fig. '7 is a. sideelevation, partly'in section and with parts broken- 'away fof thefingers and connecting member shown in Fig; 6.

In the furnace shown in Fig. 1, a plurality of vertically .spac'ed-iandsubstantially circular hearths'are provided-as'at-JO, H and I2. Thesehearths are surrounded and-supported in aconventional manneribyzasubstantially cylindrical furnace Wall 132 A'rotatable'shaft l4is'mounted vertically at .lthe" center of the hearth's. To the shaft areattacheda pluralityiof'rabble arms Ilia, 151),: 15c? and.- *l5d 3havingattached thereto depending te'eth .16 :somouhted as gradually. to .movethe chargeradia'lly. of the hearths as the rabble arms'slowly rotate?shaftfll lxnormally consists of a plurality of superposed .;tubular'..members, :each having, an .outel. tubular f'section" and an'innertubular section, the latter-conducting: coolingfair tothe rabble1arms"'as.labove mentioned. 'It is, of course, possible toiemployionly asingle tubularmember.

1A chargestofbetroastedlis introduced; into the ,furnace atitstopgpassingsuccessivelydownward under the::influen"ce' of gravity andthe Push .of..the;rabble:arriis through acentra'l openingto hearth-1| I,Ithence through-peripheral openings ;l8t,o? hearth I land then out the.central opening .19 to similar lower :hearthsior to a final passage. 1The structure and.operation thus-far described are: .old .intheiart,i;being; shown; for. example, in the patent to zDudleyBaird N 0-;1,669,925; issued .May 15.19281. :;.c.,. g Y

:In the operati n of thistype of;furnace,* ithas been gfound thatmnderhigh temperature conditions parts of, *thegc entralishaft': sometimesare jfractured.- 1'Ihis-is due usually to unequal expansion ofsuchvpart's, Theregion of the furna'ceaboutthe outersurface of'the shaftreaches high temperatures-and the. outer tubular. sections expand bothlongitudinally andeircumferentially. The inner tubularsections'ontheot'h'er hand are cooled morethairsaid outer sections bythe air circulating therein and do not reach the same hightemperature;This temperature diiferential results in an expansion 'diflerentialwherein the outer tubular: sections lengthen relativet-to' said innersections; j This-riplaces; the connecting ribs or webs lnderhighstressxsometimes to suchan extent a's'to. producea'fracturefthereof"or a frac- 3 ture of either the inner or outer tubularsections adjacent the juncture of the ribs therewith. Replacement of theshafts in prior construction has entailed considerable inconvenience andloss due to the shutting down of the furnace, and due to the fact thatentire tubular members in many cases have to be replaced. Thus thefracture of a rib usually results in an item of substantial cost.

Moreover, the radially extending rabble arms are supported jointly bythe inner and outer tubular sections. Thus a fracture of ribs results ina weakening of the support for the rabble arms and may cause them totwist relative to the supporting shaft due to loss of support of saidinner members and due to the resistance of the material which is movedby said arms. Thus a twisting of the inner shaft may occur relative tothe outer shaft. This twisting may be communicated to the unfracturedribs and damage them also.

Turning now to the novel features of our invention, Figs. 2 and 3indicate that we have constructed the shaft I4 of separate parts whichare associated in a novel manner. Outer tubular sections are shown as at20, 2| and 22. Correspending inner tubular sections are shown as at v23,24 and 25.

As above mentioned, each outer tubular section, such as 2I, willlengthen appreciably under the influence of heat by an amount greaterthan the lengthening of each cooler inner tubular section, such as 24.The sameis true concerning radial or diametric expansion. The latter isalso sometimes referred to as circumferential expansion.

This expansion differential, in structures having integral ribs, hasaffected not only the ribs interconnecting the inner and outer sectionsbut also has affected the alignment of the rabble arms. Referring. toFig. 1, it will be seen that when an outer tubular section of thecentral shaft lengthens relative to an inner tubular section, the rabblearms, for example, lid and Ic, will be misaligned as by spreading apartwhereby the proper clearances relative to the hearths will be destroyed.

Referring to Fig. 3, novel means are provided for compensating for thelongitudinally greater expansion of each outer tubular section ascomfrom the inner surface of the outer tubular section 2 I. This groupis equal in number to fingers 26. The two co-acting fingers 26, 21,comprising each pair, are held in radial alignment and clamped tightlytogether, for example, by means of a stud and bolt device 28 as shown indetail in Fig. '7. This device comprises a stud 28a having a head whichis adapted jointly to engage surfaces of the fingers 26, 21, and whichcooperates with a bolt 28b. A suitable washer 280 can be used with bolt2% to engage opposite surfaces of fingers 26, 21. The bore through whichthe shank of the stud 28a extends is formed preferably as shown in Fig.6. As indicated in Fig. 5, the finger 26 is originally formed with apointed extremity which extends into a corresponding recess originallyformed in the finger 21. However, the adjacent faces of these fingersare in spaced relationship. A joint bore is formed as at 29 in thecooperating fingers.

It is preferable to form the joint bore 29 by a drilling operation.However, this bore can be formed in the casting. The shank of the stud28a preferably is of slightly less diameter than the diameter of thejoint bore 29 in order to permit, if necessary, diametric expansion ofthe inner tubular section.

The connecting member 28 for associating the cooperating fingers '26,21, of course, can be in any suitable form, the stud and bolt devicebeing only one structure for this purpose. Each finger connecting memberholds each cooperating pair of fingers against relative longitudinal andangular movement but not against relative radial movement caused byexpansion.

It has been found desirable to locate the cooperating sets of lugsadjacent the extremities of the inner and outer tubular sections. One ofthe reasons for this is to provide easy accessibility thereto forpurposes of machining castings and for ease of assembly and disassembly.Thus a second group of outwardly extending lugs 30 is formed at theopposite extremity of the inner tubular section 24, which groupcooperates with an equal number of inwardly extending lugs 3| upon theouter section.

In view of the fact that the cooperating fingers upon the tubularsections are locked against relative axial or longitudinal movement byvirtue of their clamping or connecting members, it is desirable to severthe inner tubular section preferably at the mid-point thereof as at 24a(Figs. 3 and 4). The severance or weakening line 24a preferably is castin each inner section to facilitate the subdivision thereof into twosubsections. The fracture normally is made as by a hammer and chiselprior to assembly of the shaft. However, it is possible to allow thefracture to occur automatically when the shaft and furnace are inoperation. Thus when the outer tubular section 2 I becomes greater inlength than the inner tubular section 24, the two halves of the latterwill separate. Thus after fracture at 24a there will be no resistance bythe inner section to the expansion of the outer section. A seal isprovided at the point of fracture of said inner section 24 by means of,for example, a metal ring member or collar 32 preferably of a resilientnature which tends to expand to seal the fracture as indicated in Fig.4, whereby the air flowing through section 24 will not escape. The ringmember 32 is sometimes referred to as the expansion ring and preferablyfits within a suitable internal groove 33 formed upon the inner surfaceof the tubular section 24. Such an expansion ring can be easily movedinto position in a contracted condition. When released, it will expandinto said groove and into a desired sealing position.

The rabble arms, such as I5a, I50, are disposed near the extremities ofthe tubular sections 2|, 24 and therefore near the cooperating groups offingers or lugs 26, 21 and 30, 3|, respectively. Because of theirproximity to their respective groups of cooperating fingers, noappreciable expansion differential can occur which will misalign saidarms. That is, the distance between rabble arms I51; and the cooperatingfingers 26, 21 is 'sufficiently small so'that any expansion differentialbetween tubular'sections 2| and 24 will not disturb the alignment ofsaid arms relative to arms I5c to an undesirabledegree.

The association of the inner tubular sections :23 and 125 with.ltheir:respective:'lduterttubular sections Zfltand 22" is effected by meansidentical .tothose described for tubular sections "2| and --24.- .1Forexample,'section 22, by-meansof fingers .34. thereon,isnassociatedwith'isection 25 upon 1' fastened flanges 21a, 22aland-byvirtue of theproximityof fingers 26, 2l--and 34, 35. *In operatiomwhenithe furnaceshaft is heated within the furnace, the outer tubular sections will beheated to agreater extent than the inner tubular sections and hence willexpand both radially and longitudinally to a greater. extent than theinner tubular sections. The relatively .greater radial expansion isaccommodated by virtue of the factfthat the fingers on the .outersections can move radially away from the fingers on the inner sections.And the relatively greater longitudinal expansion is accommodated by theaxial separation 'of 'each inner tubular section into two subsections.

Instead of locking the opposite extremities of correspondinginner andouter tubular sections against relative longitudinal movement andsplitting the inner tubular section as at Ma, it is desirable under somecircumstances to clamp together only one extremity of corresponding -inner and outer tubular sections and to employ at the opposite extremity astudand shank arrangement as indicated in brokenlines in Fig: 7 whichwill so associate the cooperatingfingers that relative rotation will beprevented but some relative longitudinal motion can occur. Such a studand bolt device is indicated at 28d and differs from the one originallydescribed in that the shank or the stud is longer than that of stud 28a.If the inner and outer tubular sections are associated in this manner,it is desirable for each such section to have but one set of rabble armsthereupon and this set preferably should be mounted adjacent the tightlyheld extremities of said sections, namely, in proximity to the extremitywhich is locked against relative axial movement.

There are thus provided novel means for associating the inner and outertubular sections of a rotatable furnace shaft. The means are very simplein construction and are inexpensive to manufacture and rugged inconstruction. The novel means eliminates almost entirely the possibilityof furnace breakdown due to fracture of ribs or fingers whichinterconnect said inner and outer tubular sections. Moreover, it assuresthe maintenance of a proper alignment between rabble arms mounted on theshaft and enables the inner tubular sections to provide a driving torqueto the rabble arms without the disadvantages which normally accompany anexpansion differential between inner and outer tubular sections. Theconnecting members for holding in radial alignment cooperating fingersupon said sections insure the transmittal of a proper torque to theinner tubular sections whereby relative angular movement therebetween isprevented.

Although the invention has been described in c'ennectiomvithai-iipreferred-examples it is to be expres'sly-un e'rs'tobd' th'at theinvention is not limited theret'o. For example-instead of forming aseverance li as 'at -24d, upon each inner tubular section possibleoriginally to form each inne' sectlon in two 'separate subsections 2 7 IIn thecopendihg application--of Charles W. Nichols Ser. -No' '65l, 537,filed- March 2,1946, certain' alternative constructions are disclosedand certain featur" of the'present invention are claimed, .I' 1. 1; 1.1:'ITLQL. I... L -:.i It will be understood by those skilled in the art,after! uiiderStanding' the invention,- that various. changes andmodificati'ons' may be made without departing 'from the spirit and scopeof -.the invention, 'and it is intended therefore in the appended claimsto cover 11 such changes and modifications. l 1 What is claimed as newand-' is desired to be secured byLLettersPatent is: 1 I

-- 1. Acombination"of'parts for use in a furnace of a type having rabblearms carried bya central shaft comprising'an'inner' shaft, a pluralityof outwardly extendingflugssecure'd to said inner shaft, an outersurrounding shaft having inner wall surfaces spaced from said innershaft, a like plurality of inwardly extending lugs secured to the innerwall surfacesof-"said outer shaft, anda like plurality of members forconnecting corresponding lugs upon said inner and outer shafts forholding same "in radial aligmnent.

' 2. A combination of'parts" for usein a furnace of a type having rabblearms'carriedby' a central shaft, comprising an inner shaft, a plurality"of outwardly extending fingers secured to saidinner shaft adjacent eachextremity thereof,'an outer surrounding shaft having'the inner wallsurfaces thereof spaced'from said inner shaft, a like plurality ofinwardly extending fingers secured to the inner wall surfaces of saidouter shaft adjacent theextremities-thereof, and alike plurality offinger interconnecting members for holding in alignment correspondingfingers upon said inner and outer shafts, said inner shaft being formedinto two subsections intermediate the extremities thereof.

3. In apparatus of the class described, an inner tubular member, aplurality of outwardly extending fingers secured to said member, anouter tubular member surrounding said inner member, a like plurality ofinwardly extending fingers secured to the inner surface of said outermember, and mechanism for holding in alignment corresponding fingersupon said inner and outer members.

4. A combination of parts for use in a furnace of a type having rabblearms carried by a central shaft, comprising an inner tubular member, aplurality of outwardly extending fingers secured to said member neareach extremity thereof, an outer surrounding tubular member having innerwall surfaces spaced from said inner tubular member, a like plurality ofinwardly extending fingers secured to said inner wall surfaces near theextremities of said outer tubular member, a like plurality of membersfor holding corresponding fingers upon said inner and outer tubularmembers in radial alignment, each of said inner tubular members beingseparated into two separate sub-sections intermediate the extremitiesthereof, said sub-sections being in abutting relation when there is noexpansion differential between said inner and outer members but beingsubject to separation in response to a greater expansion of said outermember relative to said inner member, and a ring member mounted betweensaid sections for sealing the region of separation therebetween.

5. A combination of parts for use in a furnace of a type having rabblearms carried by a central shaft, comprising an inner tubular section, aplurality of outwardly extending fingers secured to said section neareach extremity thereof, an outer surrounding tubular section havinginner wall surfaces spaced from said inner tubular section, a likeplurality of inwardly extending fingers secured to said inner wallsurfaces near the extremities of said outer tubular section, and a likeplurality of members for holding corresponding fingers upon said innerand outer sections in radial alignment, said inner tubular member beingseparated into two separate sections intermediate the extremitiesthereof.

6. A combination of parts for use in a furnace of a type having rabblearms carried by a central shaft, comprising an inner tubular section, aplurality of outwardly extending lugs secured to said section, an outersurrounding tubular section having the inner wall surfaces thereofspaced from the inner tubular section, a like plurality of inwardlyextending lugs secured to the inner wall surfaces of said outer tubularsection,,and a like plurality of lug connecting members for holding eachlug upon one section in cooperation with a corresponding lug upon theouter section, each connecting member being constructed and arranged tohold each pair of cooperating lugs against relative longitudinal andangular displacement.

'7. A combination of parts for use in a furnace of a type having rabblearms carried by a central shaft, comprising an inner shaft formed oftubular sections, a plurality of outwardly extending lugs secured tosaid sections near each extremity faces spaced from said inner shaftsections, a like plurality of inwardly extending lugs secured to theinner wall surfaces of said outer surrounding tubular sections, a likeplurality of clamp members for clamping in alignment corresponding lugsupon said inner and outer tubular sections, means for securing togetheradjacent ends of said outer tubular sections, each of said inner tubularsections having a frangible portion formed circumferentially andintermediate the extremities thereof, and an expansible sealing ringmounted internally of each inner tubular section in alignment with eachfrangible portion. 7

8. A combination of parts for use in a furnac of a type having rabblearms carried by a central shaft, comprising an inner shaft formed oftubular sections, a plurality of outwardly extending lugs secured tosaid sections near each extremity thereof, an outer surrounding shaftalso formed of tubular sections having their inner wall surfaces spacedfrom said inner shaft sections, a like plurality of inwardly extendinglugs secured to the inner wall surfaces of said outer surroundingtubular sections, a like plurality of lug interconnecting members forholding in alignment corresponding lugs upon said inner and outertubular sections, and means for securing together adjacent ends of saidouter tubular sections.

CHARLES W. NICHOLS. JOSHUA GREENSPAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,464,396 Rowland Aug. 7, 19231,732,843 Halse Oct. 22, 1929 1,899,922 Black Mar. 7, 1933 2,332,387Martin Oct. 19, 1943

